GENERATIVE ORGANS OE ARTHROEODA. 



203 



partly formed from the appendages (Crustacea), or by them and 

 whole metameres (Insccta). The appendages have further many 

 other relations to the generative apparatus, for they serve as organs 

 for seizing and holding the female, and are modified accordingly. 

 The generative system is here seen to be so correlated with other 

 parts, as to be of great importance in determining the form of the 



whole organism. 



§ 227. 



Fig. 153. Gut and male generative appa- 

 ratus of Pleuroma. Side view, oe Fore- 

 gut, v Mid-gut. h Unpaired ca?cal-sac. 

 i Hind-gut. c Heart, t Tes'is. vd Coiled 

 vas deferens (after Clans). 



Among the Crustacea we meet with hermaphroditism in some of 

 the Cirripedia. The testes and ovaries are greatly ramified tubes, 

 which can only be distinguished externally by their position in the 

 body. In the Lepadidae the ovaries are placed in the stalk 

 formed by a diverticulum of the mantle ; they give off an oviduct to 

 the mantle-cavity on either side. In the Balanidse they are em- 

 bedded in the mantle. In both families the male reproductive 

 glands are disposed around the intestinal tract, and unite at each 

 side into a vas deferens, which 

 runs alongside the hind-gut, 

 and opens with its fellow of 

 the other side at the end of 

 the postabdomen. 



In the other, or dioecious 

 Crustacea, the organs of both 

 sexes are arranged in very 

 much the same manner. There 

 are two different forms of the 

 generative apparatus accord- 

 ing as the germ-gland is paired 

 or unpaired. But these are 

 connected with one another by forms in which the two germ-glands 

 are united into an organ which is externally single. 



We meet with unpaired germ-glancls in the free-living 

 Copepoda. The ovary or testis (Fig. 153, t) lies in the middle line 

 above the mid-gut (v). The ovary gives off an oviduct on either 

 side, which either takes a simple course backwards, or forms in its 

 terminal portion several coils, which function as a uterus (parasitic 

 Copepoda) ; or it may be beset along its whole course by a large 

 number of diverticula (Fig. 154, B), which hold the eggs (Corycasidas). 

 The short terminal portion has either glandular walls, or is provided 

 with a special cement glnnd. An enlargement of the terminal 

 portion functions as a receptaculum seminis, and in many cases, as 

 for example in the Siphonostoma, may form a special tract, pro- 

 viding a special orifice for the reception of the sperm. In many 

 Siphonostoma the ovary is double ; but the two ovaries are often 

 placed close together. We find the same in the male Copepoda, 

 when the free-living forms have a simple testis, and the Coryca3ida3 

 have one divided into two halves, which pass on either side into a 

 special vas deferens. In many families the right seminal duct is 



